This invention is directed to a lens for use with safety glasses and more particularly to a prescription lens for safety glasses which is snapped onto the inside surfaces of the frame for safety glasses. Thus, the safety glasses can be made plain without a prescription wherein the prescription safety glass lenses are made for a specific person and secured onto the inside of the glass frame.
Heretofore supplemental lenses have been used for various types of glass frames which include regular glass and masks. Such known glasses include an adhesive bifocal lens U.S. Pat. No. 5,153,619. A thin plastic membrane which is applied to a spectacle U.S. Pat. No. 3,628,854. German patent 2,923,798 is directed to swim goggles to which corrective lenses have been bonded. U.S. Pat. No. 4,717,249 illustrates a prism lens applied to a mask for improved vision. U.S. Pat. No. 4,563,065 shows a multiple lens from which separate lenses can be torn off for use in a mask. The lens has means for securing the lens in a mask. French patent 1,489,383 sets forth a foldable lens which is attached to the temple of a frame. Other lenses are available and can be used with glasses or masks.
Two pair of prior art glasses have become known which are of interest. One pair of glasses makes use of a frame which has an outward projecting rim along the inner surface of the lens which forms a recess substantially around the frames excepting in a center upper portion. The insert has a sloping edge which snaps under the projecting rim in order to hold the insert on the inside of the frame. The insert fits under the projecting rim and is held in place by a snap fit. The other pair of glasses has a projecting rim entirely around the inside of the frame surrounding the main lens. The frame has a center top projection with a central protrusion under which a U-shaped portion of the rim of the insert fits. The remaining portion of the insert has a sloping rim surface which snaps into the projecting rim of the frame so that the inert snaps under the projecting rim and under the projecting upper center piece.